Brake mechanism



July 16,1935. H. c. BOWEN BRAKE MECHANISM Filed Jan. 9, 1951 1 7714972222".- I Zrarf 6.50206E flm Patented July 16,1935 2,008.385

UNITED STATES PATENT OFFICE BRAKE MECHANISM Herbert C. Bowen, Detroit, Mich., assignor to Hydraulic Brake Company, Detroit, Mich., a

corporation of California Application January 9, 1931, erial-No. 507,631

14 Claims. (Cl. 188152\ The invention relates to braking systems for For the purpose of illustrating and describingmotor vehicles or the like and more particularly my invention I have shown the same operating to abrake applying mechanism associated with in connection with a fluid operated brake system the brake foot pedal of thevehicle for effecting a such as is illustrated and described in a Patent gain or increase'in leverage over that which is No. 1,758,671, issued to Malcolm Loughead, May '5 applied by the brake pedal. 13, 1930.

In a brake mechanism for motor vehicles or In the drawing I have shown the braking systhe like the leverage applicable to the brakes of a tem more or less schematically and in which a motor vehicle is directlyjproportional to the fluid reservoir 2 is shown in communication with .amount of available brake pedal travel and it is the mastercylinder 3 (shown dotted) which lies 10 thus apparent that the pressure and stroke dewithin the reservoir 2. The master cylinder 3 termine the total energy available in the applicahas a piston 4 reciprocally supported therein for tion of the brakes. Various methods have been the purpose of supplying a fluid pressure through devisedto overcome this lack'of suificient lethe conduits 5 to the brake cylinders 6 having verage by the use of booster systems. by which pistons 6 for moving the shoes l5 into frictional 5 they are commonly known. Certain characterengagement with the brake drum 6 The brake istics in systems of this type are, however, undepedal 9, when depressed, transmits movement to sirable, such as the lag in the application of the the lever I supported on the shaft 8 through the booster mechanism when the brake pedal is deagency of the levers l0 and H and the link I2.

pressed and its failure to, assist in the application This movement of the lever l actuates the piston 20 of the brakes until a high brake pedal pressure is 4 to provide fluid pressure for the aforesaid purreached, with the result that its efficiency is deposes. The lever I0 is pivotally secured at its creased as the pedal pressure is increased. one end to the shaft 8 and at its opposite end to It is to this end that I have devised a braking the upper end M of the arcuate portion 15 of system which overcomesthe undesirable characthe lever II by a pin [6. The link I2 which con- 25 teristics, and an object of my invention is the nects the brake pedal 9 to the lever II is secured provision of means which-become effective the at its opposite ends to thimbles I'l pivotally seinstant that the brake pedal pressure is applied cured, respectively, to the brake pedal and an and act to permit an increase in leverage with a intermediate portion of the lever ll.

predetermined brake pedal travel over that in- A cylinder i8 is provided with a reciprocally 30 itiallyexerted by the brake pedal. mounted piston is which is influenced by the de- Another object of my invention is the propression in the intake manifold 2|.of the motor vision of a combination of levers which, upon the vehicle. The cylinder I8 forward of the piston application ofpressure of the brake pedal, func- I9 is connected to the manifold 2| by the conduits tion instantly to apply pressure to the braking 20 and 23 through an interposed valve 22., the 35 system. 4 opening and closing of which is under the control A further object of my invention is the proof the brake pedal 9. The exhaustion of the vision of a device operated by energy supplied cylinder 18 forward of the piston l9 permits air by the motor of the vehicle for shifting the pivunder atmospheric pressure to enter the cylinder otal point of a certain one of the combination of to the rear of the piston l9 through an aperture 40 levers upon a partial operation of the brake pedal 24 to force the same to the right with reference to increase the available leverage for a predeto the drawing, against the tension of the termined travel of the brakepedal. spring 25.

A still further object of my invention is the A connectingrod 26 for the piston l9 extends 46 provision ofadevice operated by energy supplied forward of the cylinder I8 and a thimble 21 by the motor of the vehicle and under the control pivotally secured to the end 28 of the lever I I of the brake pedal to shift a certain one of the serves to connect the rod 26 to the lever H. The combination of levers to permit an increase in fulcrum 35 against which the lever ll normally physical leverage for a predetermined amount of rests serves as a fulcrum about which the lever pedal travel. ll operates during initial movement of the brake 50 With these andother objects in view, the inpedal 9 to efiect movement of the lever I. The

vention consists of-novel details of construction lever ll, upon the opening of the valve 22, is and arrangement of parts as will be more fully also moved under the influence of the piston l9 hereinafter disclosed and particularly pointed V inthe cylinder It to disengage the fulcrum point out in the appendedclaims. 35, and further movement of the lever H'bythe 5 lever Ill. The piston i9, upon reaching the limit of its stroke, arrests further movement of the lever about the fulcrum 30 to shift the fulcrum about which the lever II will now operate to the pivotal point 3| between the lever II and the rod 26. This pivotal point thereafter serves as a fulcrum about which the lever operates to bring about further movement of the lever I. The leverage thus applied to the lever 1 during this portion of the movement of the lever about the fulcrum 3| is greatly increased as will be more fully hereinafter described.

The cylinder 8 is connected to the intake manifold 2| of the motor through conduits Hand 23 and valve 22 which is operatively associated with the brake pedal. The valve stem 32 of the valve 22 is normally engaged by a lug 33 onthe brake pedal 9 to maintain the valve 22 normally closed, thus maintaining the cylinder l8 under atmospheric pressure through the valve 22. The valve, when opened by the movement of, the brake pedal 9, shuts off the air and connects the cylinder 8 to the intake manifold 2| through the conduits 20 and 23. The valve" 22 may be of any approved type such' as illustrated and described in an application of C. C. Bradbury, filed December 21, I929, Serial No. 415,648 now Patent No. 1,899,009, issued February 28, 1933.

The lever I, when in normal position rests' against an adjustable stop in the form of a screw stop 35 adjustably mounted in 2, lug 38 integrally formed with the reservoir 2 and serves. as a fulcrum about which the lever operates as has already been pointed out in a general way and which will be more fully described later in the description. 1

Having described the various elements that go to make up my improved brake applying mechanism, I will now point out more fully its application for increasing or multiplying the leverageof the force applicabl to the lever I for a predetermined travel of tl% brake, pedal 9. It is well known that the levera e obtainable by manual operation is directly proportional to the amount 'of brake pedal travel available and as this amount of travel is limited it is not practical to increase the brake pedal travel proportionate 'to the increased weight or speed of the motor vehicle, though high leverage is most essential for efficient brake performance of the motor vehicle. With theseobjects in view I have devised a new and novel method of increasing the leverage obtainable for a predetermined travel of the brake pedal 9 The brake applying mechanism of my invention makes use of the vacuum cylinder I8 for the purpose of transferring the fulcrum about which the lever operates upon the initial movement of the brake pedal 9 to a second fulcrum and the continued pressure of the brake pedal 9, then, is multiplied through levers l and II with the lever moving about the fulcrum 3| as will be pointed out later.

The manner in'which the change of leverage occurs may be briefly described as follows: In its normal position the lever rests against the stop 35 so that the, stop 35'constitutes the fulcrum around which the lever I operates before the pedal 9 has moved a distance sufilcient to release the valve 22. When the lever has released the valve 22, the. suction in the cylinder |8 causes the piston -|9 to move forward rapidly. During this forward movement of the piston ill, the

of the brake pedal 9 in'a'brake applying direction,

the lever fulcrums about the pivot 3|. Thus it will be seen that the lever during the application of the brakes, fulcrums first about the stop 35, next about the pivot 30, and lastabout the pivot 3|. Theoperation of the entire mechal5 nism will now be more fully described.

When the driver of the vehicle depresses the brake pedal 9 the initial movement of the same to the left, with reference to the drawing, causes the link l2 to move the lever about the stop 35 as a fulcrum to move the lever Ill forward. This initial movement of the lever l0 rotates the shaft 8 to swing the lever lto the'right, thus forcing the piston 4 into the master cylinder 3 to displace the fluid therein. Theinitial movement of the pedal 9 also causes the lug 33 thereon to disengage the valve stem 32 of the valve 22 to open the same. The valve 22, having opened the cylinder 8, is 'now connected to the manifold 2| of the motor and the depression maintained' therein by the operation of themotor causesthe withdrawal of air from the cylinder l8. As the space forward of the piston I9 is being evacuated air under atmospheric pressure enters the cylinof the piston I9, causing the same to move to the right rapidly against the normal compression of the spring 25. This rapid movement of the piston l9 moves the arm away from the stop about thefulcrum 30. As the movement of the 0 piston l9 continues the lever H is drawn away from the stop and the lever II, when thus disengaged from the stop 35, operates about the pivotal point 30 to cause further forward movement of the lever It to actuate the lever I.

The movement of the lever about the fulcrum 3|! continues as just described until the piston I9 reaches the limit of its stroke when further movement of the lever about the fillcrum 30 is arrested. The instant the movement '50 of piston ,|9 is arrested, the pivotal point 3| between the lever and the rod 26 becomes a fulcrum. about which the lever operates until the'movement of the lever to 'the left as viewed in the drawing is arrested by discontinuing the.

operation of the pedal lever 9 or by the engagement of the lever l-l with the stop 35. I

The movement of the lever about the stop 35 upon the initial movement of the brake pedal 9 and its subsequent movement about the fulcrum 30 while the piston is moving to the end of its stroke, causes the lever to move forward and operate the lever 1 to actuate vthe piston 4, thus building up a fluid pressure which is discharged der l8 through the aperture 24 located to the rear 35 through the conduits 5 into the brake cylinders 8' to take up the slackin the system during th initial movement of the pedal 9. Pressure upon the brake pedal 9 after the piston 9 has reached the limit of its stroke,-causes the lever II tooperate about the pivotal point. 3| as a fulcrum.

This continued pressure on the brake pedal is multiplied through the leverage of the lever and lever ID as applied to lever 1. If, for any reason, the vacuum for operating the piston |9 in the cylinder |8 fails, the application of pressure to the brake pedal 9 will cause the lever II to operate about the stop 35 as a I fulcrum during the full pressure stroke of the brake pedal 9 to move the lever l forward. This forward movement of the lever I0 causes lever I to actuate the piston 4 in the master cylinder 3 to displace fluid therein and actuate the brake system.

While I have illustrated and described the leverage change mechanism for effecting a gain or increase in leverage over that applied, operatively associated with a typical hydraulic braking system, I do not, however, wish to limit its application to braking systems. Neither do I wish to be limited to the exact structure as shown as changes and modifications may readily suggest themselves, and I therefore aim to cover all such changes and modifications as come within the spirit and scope of the appended claims.

Having described the nature and embodiment of my invention, what I claim and desire to secure by United States Letters Patent is:

1. In a hydraulic brake system including a master cylinder, a piston in said master cylinder, a lever for actuating said piston, linking means connected to said lever and having a plurality of fulcrums providing leverages for transmitting forces to said lever, a manually operable brake pedal adapted to operate said linking means about a said fulcrum during initial movement of said brake pedal and about another said fulcrum upon a subsequent movement of said brake pedal, saidlinking means being arranged to provide a greater mechanical advantage when operated about the second said fulcrum than when operated about the first said fulcrum, and operable means operated upon the initial movement of said manually operable brake pedal to operate said linking means during the interim between such initial and subsequent movements of said brake pedal for shifting from the first said fulcrum to the second said fulcrum whereby to increase the mechanical advantage afforded by said linking means for such subsequent movement of said brake pedal.

2. In a hydraulic brake system including a master cylinder, a piston in said master cylinder,

and a lever for actuating said piston, linking means having a plurality of fulcrum's for providing different mechanical advantages for the operation of said lever, a manually operable brakepedal adapted to operate said linking means about at least two of said-fulcrums providing different mechanical advantages, and suction operated means for. shifting the fulcrum of said linking means from that providing. a lesser mechanical advantage to that providing a greater mechanical advantage while said brake pedal is being operated to apply the brakes.

3. The combination with ahydraulic brake system of a manually operable brake pedal for controlling said system, linking operating connections adapted to provide difierent mechanical advantages for applying the brakes by said brake pedal, and suction operated means for operating said linking connections whereby to supplement the initial braking effort of said brake pedal at a lesser mechanical advantage and to operate said linking connections to obtain a. greater mechanical advantage for the subsequent operation of said linking c0nnecti0ns by said manually operable brake pedal."

4. In hydraulic transmission. mechanism including a fluid conduit system, braking mechanism connected with said system and operable in response to variations in pressure of the fluid in said conduit, means for varying the pressure of the fluid in said conduit, a lever for operating the last said means, manual means for operating said lever, and separately operated means for increasing the mechanical advantage afforded by said lever.

5. In a hydraulic brake system including a brake pedal, a master cylinder, a piston in said master cylinder, and an actuating lever for said' '6. In a hydraulic brake system including a I master cylinder, a piston therein, and a brake pedal for operating'said piston, a linkage operable by said brake pedal to actuate said piston, said linkage having a plurality of fulcrums to provide a mechanical advantage for transmitting the force from said brake pedal to said piston during an initial movement of said brake pedal and to provide a greater mechanical advantage for transmitting the force from said brake pedal to said piston during a subsequent movement of said brake pedal, and means responsive to the initial movement of said brake pedal for shifting from a said fulcrumto another said fulcrum, whereby to change the leverage and the mechanical advantage for transmitting the force from said brake pedal to said piston.

7. In a braking system of the class described, the combination of brake drums, braking elements adapted to be brought into engagement with said drums, operating mechanism including a lever for engaging said elements with said drums in response to a force exerted by an operator, and suction operated means for shifting the fulcrum of said lever to increase the mechanical advantage afforded by said lever for the force applied by the operator;

8. In a braking system for a vehicle having an internal combustion engine, the combination of elements adapted to be brought into braking engagement with each other to retard the motion of the vehicle, operating mechanism including a lever for engaging said elements responsive to a force exerted by the operator of the vehicle, and means actuated by the vacuum created in the intake manifold of the internal combustion engine for increasing the mechanical advantage af forded by said operating mechanism and for s1,- multaneously taking up the slack in the braking system.

9. In a brake applying mechanism for applying braking pressure in a hydraulic brake system, a manually operable pedal, a suction operated member controlled by said pedal and adapted to operate immediately upon initial movement of said pedal, and a linkage for'transmitting forces from said pedal'andsaid suction operated mem- -ber to the hydraulic brake system, said linkage advantage after the operation of said linkage by said suction operated member.

10. A brake applying mechanism for increasing the mechanical advantage of the braking force applied by an operator to increase the pressure in a hydraulic brake system, comprising a linkage the said linkage before and after said suction operated element has actuated said linkage to increase the mechanical advantage afiorded there- A brake applying mechanism for supple-' mentingthe initial effort of an operator and for improving the mechanical advantage of the braking force applied by an operator to increase the pressure in a hydraulic brake system, comprising a linkage having a plurality of fulcrums providing leverages for transmitting forces to operate the brake system, said linkage being capable of manipulation to improve the mechanical advantage afforded by it, a manually operable brake pedal for operating said linkage in applying the brakes, and means controlled by said pedal for operating said linkage immediately upon initial movement of said brake pedal in applying the brakes, said means being adapted to manipulate said linkage during such operation thereof where- 'by the mechanical advantage afforded ,bysaid linkage is greater after such manipulation than it was before such manipulation.

12. In brake mechanism of the class described,

6 adapted to be brought into engagement therewith,

power transmission mechanism for applyingsaid shoe, a lever for operating said mechanism,

manual means for operating said lever, and sepa rately operated means for increasing the mechanical advantage afiorded by said lever.

13. In combination with a vehicle having an internal combustion engine, a rotatable membena second member adapted to be movedinto and out of engagement with said rotatable member, a manually operable lever for controlling said sec ond member, operating connections between said second member and said lever adapted to provide differentmechanical advantages for applying said second member by said lever, a vacuum cylinder connected with said internal combustion engine as a source of suction, means operated by said cylinder to shift said operating connections to provide greater mechanical advantage between said lever and said second member, and means for controlling communication between said cylinder and said engine.

14. In a hydraulic transmission mechanism for a vehicle having an internal combustion engine, a fluid pressure conduit system, a motor mechanism connected with said system and operable in response to variations of pressure of the fluid in the conduit system, means for varying the pressure of r the fluid in said conduit system, a manually actuated lever for operating the last said means, suction operated means for increasing the mechanical advantage afiorded by said lever, a connection between said suction operated means and said internal combustion engine, and control means for said suction operated means.

HERBERT c. nowEN. 

